Regulatory T cells form stable and long-lasting cell cluster with myeloid dendritic cells (DC)

Identification of Candidate Immune System MicroRNAs Differentially Found in Colostrum and Milk Exosomes

BACKGROUND

The fetus grows in a sterile womb environment. After birth, the newborn immune system has two immediate hurdles to clear. First immediate suppression of the womb compatible immune system and turn on the immune system of the newborn that can counter the antigenic world. The underlying mechanism of immune fluctuation by milk microRNAs (miRNAs) can be crucial for the treatment of critical or premature newborn.

METHODS

We collected fourteen samples of each colostrum and mature milk from lactating mothers, four samples of each were used for microarray analysis, and the other ten were used for miRNA expression profiling by real-time PCR.

RESULTS

From the microarray, 154 differentially expressed miRNAs were identified, whereas 49 miRNAs were revealed as immune-related miRNAs based on a literature study. Among the 49 miRNAs, 33 were already shown as strongly validated immune-related miRNAs (validated by qPCR, Western Blot, and Luciferase assay) and were considered for further analysis. Twenty-two miRNA expressions were analysed by real-time PCR as their Ct values were within considerable limits. Twelve numbers of miRNAs were significantly downregulated in mature milk compared to colostrum, which were again subjected to bioinformatics analysis to predict the biological mechanisms behind the differentially expressed miRNAs.

CONCLUSION

This study shed light on the human milk exosome miRNA expression dynamics during lactation and their possible role in the gradual skewing of the newborns' immune system. The information is crucial for the development and onset of sepsis in premature newborns in the NICU.

Delineation of colorectal cancer ligand-receptor interactions and their roles in the tumor microenvironment and prognosis

BACKGROUND

Immunotherapies targeting ligand-receptor interactions (LRIs) are advancing rapidly in the treatment of colorectal cancer (CRC), and LRIs also affect many aspects of CRC development. However, the pattern of LRIs in CRC and their effect on tumor microenvironment and clinical value are still unclear.

METHODS

We delineated the pattern of LRIs in 55,539 single-cell RNA sequencing (scRNA-seq) samples from 29 patients with CRC and three bulk RNA-seq datasets containing data from 1411 CRC patients. Then the influence of tumor microenvironment, immunotherapy and prognosis of CRC patients were comprehensively investigated.

RESULTS

We calculated the strength of 1893 ligand-receptor pairs between 25 cell types to reconstruct the spatial structure of CRC. We identified tumor subtypes based on LRIs, revealed the relationship between the subtypes and immunotherapy efficacy and explored the ligand-receptor pairs and specific targets affecting the abundance of tumor-infiltrating lymphocytes. Finally, a prognostic model based on ligand-receptor pairs was constructed and validated.

CONCLUSION

Overall, through the comprehensive and in-depth investigation of the existing ligand-receptor pairs, this study provides new ideas for CRC subtype classification, a new risk screening tool for CRC patients, and potential ligand-receptor pair targets and pathways for CRC therapy.

The blood cells in NSCLC and the changes after RFA

Lung cancer has attracted a lot of attention because of its high morbidity and mortality. The emergence of RFA provides a new treatment for unresectable NSCLC patients. In addition to killing in situ lung tumors, RFA also provides new immuno-activated antigens, for the treatment of lung cancer. It changes the tumor microenvironment and activates the entire immune system of patients. The peripheral blood cell count is easy to achieve and the blood cells are important in tumor immunity, which changes after RFA. On the one hand, the changes in blood cells identify the immune changes of NSCLC; on the other hand, it provides support and suspicion for the treatment of RFA.

αII-spectrin in T cells is involved in the regulation of cell-cell contact leading to immunological synapse formation?

T-lymphocyte activation after antigen presentation to the T-Cell Receptor (TCR) is a critical step in the development of proper immune responses to infection and inflammation. This dynamic process involves reorganization of the actin cytoskeleton and signaling molecules at the cell membrane, leading to the formation of the Immunological Synapse (IS). The mechanisms regulating the formation of the IS are not completely understood. Nonerythroid spectrin is a membrane skeletal protein involved in the regulation of many cellular processes, including cell adhesion, signaling and actin cytoskeleton remodeling. However, the role of spectrin in IS formation has not been explored. We used molecular, imaging and cellular approaches to show that nonerythroid αII-spectrin redistributes to the IS during T-cell activation. The redistribution of spectrin coincides with the relocation of CD45 and LFA-1, two components essential for IS formation and stability. We assessed the role of spectrin by shRNA-mediated depletion from Jurkat T cells and show that spectrin-depleted cells exhibit decreased adhesion and are defective in forming lamellipodia and filopodia. Importantly, IS formation is impaired in spectrin-depleted cells. Thus, spectrin may be engaged in regulation of distinct events necessary for the establishment and maturity of the IS: besides the involvement of spectrin in the control of CD45 and LFA-1 surface display, spectrin acts in the establishment of cell-cell contact and adhesion processes during the formation of the IS.

Strong adhesion by regulatory T cells induces dendritic cell cytoskeletal polarization and contact-dependent lethargy

Chen et al. show that regulatory T cells adhere to dendritic cells (DCs) with high binding forces. This strong binding causes cytoskeletal polarization in the latter, which limits DCs’s ability to form productive engagement with other antigen-specific T cells.

Dendritic cells are targeted by regulatory T (T reg) cells, in a manner that operates as an indirect mode of T cell suppression. In this study, using a combination of single-cell force spectroscopy and structured illumination microscopy, we analyze individual T reg cell–DC interaction events and show that T reg cells exhibit strong intrinsic adhesiveness to DCs. This increased DC adhesion reduces the ability of contacted DCs to engage other antigen-specific cells. We show that this unusually strong LFA-1–dependent adhesiveness of T reg cells is caused in part by their low calpain activities, which normally release integrin–cytoskeleton linkage, and thereby reduce adhesion. Super resolution imaging reveals that such T reg cell adhesion causes sequestration of Fascin-1, an actin-bundling protein essential for immunological synapse formation, and skews Fascin-1–dependent actin polarization in DCs toward the T reg cell adhesion zone. Although it is reversible upon T reg cell disengagement, this sequestration of essential cytoskeletal components causes a lethargic state of DCs, leading to reduced T cell priming. Our results reveal a dynamic cytoskeletal component underlying T reg cell–mediated DC suppression in a contact-dependent manner.

Engagement of distinct epitopes on CD43 induces different co-stimulatory pathways in human T cells

Co‐receptors, being either co‐stimulatory or co‐inhibitory, play a pivotal role in T‐cell immunity. Several studies have indicated that CD43, one of the abundant T‐cell surface glycoproteins, acts not only as a potent co‐receptor but also as a negative regulator for T‐cell activation. Here we demonstrate that co‐stimulation of human peripheral blood (PB) T cells through two distinct CD43 epitopes recognized by monoclonal antibodies (mAb) CD43‐6E5 (T_6E5‐act) and CD43‐10G7 (T_10G7‐act) potently induced T‐cell proliferation. However, T‐cell co‐stimulation through two CD43 epitopes differentially regulated activation of nuclear factor of activated T cells (NFAT) and nuclear factor‐κB (NF‐κB) transcription factors, T‐cell cytokine production and effector function. T_6E5‐act produced high levels of interleukin‐22 (IL‐22) and interferon‐γ (IFN‐γ) similar to T cells activated via CD28 (T_CD28‐act), whereas T_10G7‐act produced low levels of inflammatory cytokines but higher levels of regulatory cytokines transforming growth factor‐β (TGF‐β) and interleukin‐35 (IL‐35). Compared with T_6E5‐act or to T_CD28‐act, T_10G7‐act performed poorly in response to re‐stimulation and further acquired a T‐cell suppressive function. T_10G7‐act did not directly inhibit proliferation of responder T cells, but formed stable heterotypic clusters with dendritic cells (DC) via CD2 to constrain activation of responder T cells. Together, our data demonstrate that CD43 is a unique and polarizing regulator of T‐cell function.

Enhanced renewal of regulatory T cells in relation to CD4(+) conventional T lymphocytes in the peripheral compartment

CD4(+) Foxp3(+) regulatory T (Treg) cells are necessary for the maintenance of self-tolerance and T-cell homeostasis. This population is kept at stable frequencies in secondary lymphoid organs for the majority of the lifetime, despite permanent thymic emigration or in the face of thymic involution. Continuous competition is expected to occur between recently thymus-emigrated and resident Treg cells (either natural or post-thymically induced). In the present work, we analysed the renewal dynamics of Treg cells compared with CD4(+) Foxp3- conventional T cells (Tconv), using protocols of single or successive T-cell transfers into syngeneic euthymic or lymphopenic (nu/nu or RAG2(-/-)) mice, respectively. Our results show a higher turnover for Treg cells in the peripheral compartment, compared with Tconv cells, when B cell-sufficient euthymic or nude hosts are studied. This increased renewal within the Treg pool, shown by the greater replacement of resident Treg cells by donor counterparts, correlates with augmented rates of proliferation and is not modified following temporary environmental perturbations induced by inflammatory state or microbiota alterations. Notably, the preferential substitution of Treg lymphocytes was not observed in RAG2(-/-) hosts. We showed that limited B-cell replenishment in the RAG2(-/-) hosts decisively contributed to the altered peripheral T-cell homeostasis. Accordingly, weekly transfers of B cells to RAG2(-/-) hosts rescued the preferential substitution of Treg lymphocytes. Our study discloses a new aspect of T-cell homeostasis that depends on the presence of B lymphocytes to regulate the relative incorporation of recently arrived Treg and Tconv cells in the peripheral compartment.

Multiple sclerosis associated genetic variants of CD226 impair regulatory T cell function

Recent association studies have linked numerous genetic variants with an increased risk for multiple sclerosis, although their functional relevance remains largely unknown. Here we investigated phenotypical and functional consequences of a genetic variant in the CD226 gene that, among other autoimmune diseases, predisposes to multiple sclerosis. Phenotypically, effector and regulatory CD4(+) memory T cells of healthy individuals carrying the predisposing CD226 genetic variant showed, in comparison to carriers of the protective variant, reduced surface expression of CD226 and an impaired induction of CD226 after stimulation. This haplotype-dependent reduction in CD226 expression on memory T cells was abrogated in patients with multiple sclerosis, as CD226 expression was comparable to healthy risk haplotype carriers irrespective of genetic variant. Functionally, FOXP3-positive regulatory T cells from healthy carriers of the genetic protective variant showed superior suppressive capacity, which was again abrogated in multiple sclerosis patients. Mimicking the phenotype of human CD226 genetic risk variant carriers, regulatory T cells derived from Cd226-deficient mice showed similarly reduced inhibitory activity, eventually resulting in an exacerbated disease course of experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis. Therefore, by combining human and mouse analyses we show that CD226 exhibits an important role in the activation of regulatory T cells, with its genetically imposed dysregulation impairing regulatory T cell function.

Recipient myeloid-derived immunomodulatory cells induce PD-1 ligand-dependent donor CD4+Foxp3+ regulatory T cell proliferation and donor-recipient immune tolerance after murine nonmyeloablative bone marrow transplantation

We showed previously that nonmyeloablative total lymphoid irradiation/rabbit anti-thymocyte serum (TLI/ATS) conditioning facilitates potent donor-recipient immune tolerance following bone marrow transplantation (BMT) across MHC barriers via recipient invariant NKT (iNKT) cell-derived IL-4-dependent expansion of donor Foxp3(+) naturally occurring regulatory T cells (nTregs). In this study, we report a more specific mechanism. Wild-type (WT) BALB/c (H-2(d)) hosts were administered TLI/ATS and BMT from WT or STAT6(-/-) C57BL/6 (H-2(b)) donors. Following STAT6(-/-) BMT, donor nTregs demonstrated no loss of proliferation in vivo, indicating that an IL-4-responsive population in the recipient, rather than the donor, drives donor nTreg proliferation. In graft-versus-host disease (GVHD) target organs, three recipient CD11b(+) cell subsets (Gr-1(high)CD11c(-), Gr-1(int)CD11c(-), and Gr-1(low)CD11c(+)) were enriched early after TLI/ATS + BMT versus total body irradiation/ATS + BMT. Gr-1(low)CD11c(+) cells induced potent H-2K(b+)CD4(+)Foxp3(+) nTreg proliferation in vitro in 72-h MLRs. Gr-1(low)CD11c(+) cells were reduced significantly in STAT6(-/-) and iNKT cell-deficient Jα18(-/-) BALB/c recipients after TLI/ATS + BMT. Depletion of CD11b(+) cells resulted in severe acute GVHD, and adoptive transfer of WT Gr-1(low)CD11c(+) cells to Jα18(-/-) BALB/c recipients of TLI/ATS + BMT restored day-6 donor Foxp3(+) nTreg proliferation and protection from CD8 effector T cell-mediated GVHD. Blockade of programmed death ligand 1 and 2, but not CD40, TGF-β signaling, arginase 1, or iNOS, inhibited nTreg proliferation in cocultures of recipient-derived Gr-1(low)CD11c(+) cells with donor nTregs. Through iNKT-dependent Th2 polarization, myeloid-derived immunomodulatory dendritic cells are expanded after nonmyeloablative TLI/ATS conditioning and allogeneic BMT, induce PD-1 ligand-dependent donor nTreg proliferation, and maintain potent graft-versus-host immune tolerance.

Relevance of regulatory T cell promotion of donor-specific tolerance in solid organ transplantation

Current clinical strategies to control the alloimmune response after transplantation do not fully prevent induction of the immunological processes which lead to acute and chronic immune-mediated graft rejection, and as such the survival of a solid organ allograft is limited. Experimental research on naturally occurring CD4⁺CD25^highFoxP3⁺ Regulatory T cells (Tregs) has indicated their potential to establish stable long-term graft acceptance, with the promise of providing a more effective therapy for transplant recipients. Current approaches for clinical use are based on the infusion of freshly isolated or ex vivo polyclonally expanded Tregs into graft recipients with an aim to redress the in vivo balance of T effector cells to Tregs. However mounting evidence suggests that regulation of donor-specific immunity may be central to achieving immunological tolerance. Therefore, the next stages in optimizing translation of Tregs to organ transplantation will be through the refinement and development of donor alloantigen-specific Treg therapy. The altering kinetics and intensity of alloantigen presentation pathways and alloimmune priming following transplantation may indeed influence the specificity of the Treg required and the timing or frequency at which it needs to be administered. Here we review and discuss the relevance of antigen-specific regulation of alloreactivity by Tregs in experimental and clinical studies of tolerance and explore the concept of delivering an optimal Treg for the induction and maintenance phases of achieving transplantation tolerance.